eduggs

It kind of looks like the better snow threat (at least away from the immediate cost) is Sat the 17.

ICON and RDPS are 1-4" for Saturday. We take.

I think the snow talk is referring to Saturday. Yes that's the best snow threat at this juncture. So far 18z is worse for the Sun/Mon coastal threat. You don't want shortwave troffing (concave up) northeast of the vortmax at the base of the trof. That's a recipe for a late trof evolution and OTS solution. The 12z ECMWF moved a vorticity-laden shortwave through OH and NY early Sunday, which ruined the coastal threat. The 18z NAM/ICON increased troffing (concave up) in this area. By comparison, the 12z GFS had subtle shortwave ridging (concave down) over NYS.

You don't want shortwave troffing (concave up) northeast of the vortmax at the base of the trof. That's what sabotages the coastal threat on the 12z ECMWF and that's that the 18z NAM/ICON shifted more towards. By comparison, the 12z GFS had subtle shortwave ridging (concave down) over NYS.

There aren't any GEPS or GEFS members either.

Yes snow on Saturday is more likely at this point than Sunday or Monday.

You are wishcasting. The 18z is unmistakably a shift towards the ECMWF. But the differences are relatively minor and there's still time to improve this.

Agreed (for Sun/Mon). Overlaying them 18z looks more like the ECMWF. 12z looked closer to the GFS. Not a great start to 18z.

The 18z NAM adjusted from 12z to look more ECMWF-like than GFS-like. That's not a strong start to 18z.

There is an axiom on these boards that it's wise to go with the least snowy model in the mid-range. So that would be the 12z ECMWF or 12z ICON. Seems reasonable to me.

Historically this is a great spot to be in for local snowfall ~ 4 days out. There are multiple shots of snow this weekend including a potential coastal event modeled just offshore. Many many times in the past these would shift NW in the final days to deliver a solid hit. If we weren't so snake-bit over the past several years I think there would be more excitement.

Yeah, but only slightly. And nothing to support the explosive 12z GFS solution.

I like how even thought the UK misses east with the coastal, it produces a snowy Saturday with a plowable snowfall for I-95 N&W.

The GDPS shows 3 separate periods of snow - including weekend, daytime snow! It ends up as a fairly long duration light event with moderate snow accumulations region-wide. I like that outcome a lot. The GFS shows a high-end threat. That's a beautiful coastal storm evolution with NESIS potential. Things have been trending better for 2 days, but we might have reached the end of the trend. The UK backed off and the GEFS individuals are all east of and weaker than the GFS SLP except one weaker member near ELI. You could argue it both ways, but I prefer not seeing the OP GFS west of the ensemble spread. That's a red flag.

The Jan 25 event is still in the GEFS mean. In fact it's stronger this run than last. It's a major QPF signal for 11 days out and has been for several runs. Obviously a tiny model change at initialization will propagate across the entire globe over 11 days to result in huge differences at the regional/synoptic scale.

ECM-AI is west of 18z with the SLP and sharper with the trof. It's a scraper now. Very consistent trends across guidance. That's a solid improvement. 18z was well offshore and barely had a discernible coastal SLP. 0z forms a low and tracks it east of the benchmark.

I agree the 1-3" characterization is better. But the event is not quite over for I-95 by 120hrs on the UK. But only a few hundredths of QPF after.

I don't really believe in ceilings, especially beyond 24 or 48 hours or so. I remember Feb. 11, 2006 looked like a miss or fringe event 4 days out. 2 days out it looked like a plowable snowfall with a fantasy ceiling of maybe 8". Then the storm dropped 27" at NYC. If the synoptic scale features break right and the small-scale stuff aligns perfectly, sometimes there is no ceiling.

The GEFS improved again for Sunday (trof and individual members) even if QPF doesn't fully reflect the improvement.

The UK is similar to the GFS, but better. Accumulating snow to the coastal plain just NW of NYC. Nice h5 and surface almost as good as GFS-AI. Great 0z.

I'm not really sure what fast flow means here in context. In the past I think it referred to an anomalously strong jet stream across the Pacific that penetrated the North American continent with mild air. "Fast flow" seems to have become a scapegoat when anything fails regardless of cause. In this case the flow is straight out of central Canada and the flow looks seasonably fast, i.e., not too fast. The speed of a SLP is partly dependent on steering currents but also on the structure and degree of maturity of a trof. For example, a SLP may slow and stall near a cutoff upper level low even if the associated jet has winds speeds over 80 knots.

I think the 0z GFS is now one decent step away from a plowable snowfall. Last run it was 2 steps away. It's at least starting to look plausible when you loop 500mb

The GFS still isn't great for Sunday. A little 12z Canadian like with a mid-level low in the Lakes and a pos tilted trof structure

The GFS at 84hrs looks like it has a sharper shortwave with more vorticity crossing into North Dakota. I think that's the vorticity that sharpens the base of the trof a day or so later... we'll see... could be a slightly better trof for Sunday

Snows for 30 hours N&W of NYC on the ICON. Seems unlikely but fun to look at. A 6 hour period of steady rain or snow with flurries or light rain with the initial week overrunning seems more plausible.